Acknowledged datagram services are being considered by several standardization bodies for the data link layer. The performance analysis, based on simulation results of two possible implementations of such a service by using an IEEE 802.4 token-bus MAC (medium-access control) sublayer, is presented. The two implementations include immediate acknowledge (where the acknowledge has to be received before passing the token), and delayed acknowledge (where the acknowledgement can be sent only when the receiver holds the token).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>